When forming pouches or other bag from various films, a step in the forming process often entails pressing layers of film between heated sealing bars to seal one or more sides or edges of the pouch. In industrial scale operations, a continuous stream of pouches must be processed at relatively high speed, requiring frequent and accurate reciprocal movement of the sealing bars. One example of an apparatus for driving sealing bars in a pouch/bag forming process can be seen in WIPO Publication WO2012/031877, the contents of which are herein incorporated by reference in their entirety. While such apparatus have performed effectively, further improvements are possible.